Manufacture of porous ebonite bodies



Feh, l93l'. M; WILDERMAN 1,791,437

. MANUEACTURE OF POROUS EBQNITE BODIES Original FledAprl 22. 1922.

INVENTOR Patented Feb. 3, 1931 UNITED STATES PATENT OFFICE MEYEErVJILDERMAN, OF LONDON, ENGLAND, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THEAMERICAN WIEDER/MAN POROUS EBONITE COMPANY, INC., OF PHILADELPHIA,PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA MANUFACTURE OF POROUSEBONITE BODIES Original application iiled April 22, 1922, Serial No.556,088, and in France March 15, 1922. Divided and this applicationfiled October 11, 1927.

r'lhis invention relates to the production of porous bodies such asdiaphragme, filters or the like, from ebonite. It is a division of mycopending application Serial No. 556,088, filed April 22nd, 1922, whichmatured into Patent No. 1,651,567, granted December 6, 1927.

Various materials have been proposed for the construction of diaphragmeor ilters. For example, it has been proposed to use nitrocloth, cement,ceramic materials, asbestos, and various other substances. Suchdiaphragms are open to numerous objections. Many of them will notwithstand the action of alkalies, acids or chlorine. Many of them arelacking in the desired physical qualities and are likelyto become softin water, or to swell and lose their mechanical strength. Others becomebrittle and lose their strength in this way. Others cannot be made tothe desired shape, or cannot be produced straight enough to form largesurfaces. Many of them present great diiculties in manufacture and areof such character that they cannot be reinforced with a metal,particularly an insulated metal. Such diaphragms are also undesirable inthat their porosities can be varied only within comparatively narrowlimits. This restricts the {ield of useful ap` plication of the diderentdiaphragme.

In my Patent No. 1,651,567 above referred to, there is' disclosed aprocess of making diaphragms from ebonite by bringing ebonite particlesWhose surface portions at least are only partially cured, into suchvolume that the particles are in contact, but have interstitial spaces,and "vulcanizing the mass. The diaphragm thus produced is mechanicallystrong, will retainv its shape and strength under extremely adverseconditions, may be manufactured at relatively low cost, may be readilyreinforced with metal and may be made of any desired porosity, so thatits percolation rate may be varied under a wide range. Y

The present application relates to a modiled `process wherein eboniteparticles are coated with a rubber compound capable of being cured intoebonite, are then brought into such. volume as will cause the adj acontSerial No. 225,569.

particles to Contact and combine, but will not compact them into anon-porous mass, and are then vulcanized into an integral body.

As these porous bodies may be made of any desired thickness, size andshape, of any desired porosity and percolation properties, and since theebonite adheres to iron and kother metals as Well as to metals which arepartially or entirely covered with ebonite, it will be seen that theirfield of application is very great, and that theymay be .used underwidely varying conditions. .Itis pos sible, for example, to use veryporous diaphragme of great percolation properties as supports for otherdiaphragme or filtering materials, such as sand, barium sulphate, iiocksof asbestos, etc. In the latter case, the asbestos takes up alltheimpurities while the ebonite diaphragm permits Vof using the lilter fora longer time. If desired, the ebonite body can be so shaped as tocontain the other filtering material. The diaphragms also -can be soconstructed that their surfaces are especially suited for the receptionof other finely divided substances, such as barium sulphate, Portlandcement, colloids, etc. In this way it is possible to ill up thecapillaries only in the uppermost diaphragm layer with such substances,while the rest of the diaphragm retains its original high porosity andsmall electric resistance. In this way,

Vdiaphragms having a very small speed of percolation can be obtained. Anexample of this is as follows 4 A diaphragm seven millimeters thick wasprepared from line powder, the powder consisting of vulcanized hardebonite particles covered with a very thin layer of non-vul canizedebonite. The diaphragm had a` porosity of 43% and an absolutecoefficient of percolation (water at 13 C.) K=0.206. A paste of tinenatural barium sulphate was prepared and rubbed into the pores of thetop surface of the diaphragm with a piece of cloth; This reduced theabsolute coeihcient of percolation very greatly, K having become equalto 0.0001907.

In the accompanying Vdravvings which illustrate an apparatus circulardiaphragme, i

Figure 1 is a sectional view of' a mold, and

Figure 2 is a plan view thereof.

In the drawings there is shofn mold having a body portion 2 Withvdang-es 3 thereon. Bolts 4 project from the flange. A cover portion 5tits into the mold i2. This cover has sides 6 with flanges '.7 formedthereon. These flanges have holes to receive the bolts el. The coversborra as being reinforced with ribs 8.

In making a porous diaphragm in the mold, a quantity of hard rubberparticles is coated with raw rubber so that there is a thin layer ot'vulcanizable material over the surface ot the particles. The quantity ofpowder used is such that if it were com-` pressed to a solid non-porousmass having no interstices, it would form a layer in the mold ofconsiderably less thickness than t s total depth of such mold. Forexample, it the mold had a bottom area oi one square decimeter and gramsof tine ebonite poirder of specific gravity 1.25 Were used, and the moldwere subjected to a pressure of 150 atmospheres, there would result,after vulcaniz'ation, a dense ebonite plate about four n'iillimetersthick. This plate would be nonporous. Now, it the cover is so held as tobe more than fourmillimeters distant from the bottom of the mold 9 thussubjecting the material to less pressure,` there W'll be produced adiaphragm having a cert-ain degree of porosity, Which porosity Willdepend upon the thickness of the diaphra-,rin The porosity is controlledby utilizing spacers 9 Which tit over the bolts By using spacers ofdifferent length or thickness, the degree of porosity can be exactlycontrolled. For example, by using spacers so as to produce in the moldand With the material above described plates having a final thickness of5, 6, 7, 8, 10 and 12 millimeters thick instead of si. millimeters, I amable to obtain porous plates or diaphragms in which the volume of theair capillaries equals 2, 33. 50, G0 and 66% of the total volume oit theplate or diaphragm. In this rray it is possible to get porosities Whichrun through the Whole scale of the porosities ot other forms of .lia-Jhr-agnes, and still greater or smaller porosities, if desired. Stillfurther variations in porosity can be obtained by treating the surfacewith a material such as barium sulphate in the manner above described.

In making a diaphragm in the illustrated mold, the cover is put in placeafter the proper spacers have been placed over the bolts 4, and the nuts10 on the bolts are then tightened. The mold is then placed in avulcanizer and the material is cured in the usual. manner-preferably ata temperature corresponding to steam at three atmospheres pressure,although this may be varied to suit changing conditions.

Instead of using ebonite pow,r er, ebonite shavings, turnings orparticles oi" other form may be employed. The speed ot percolationthrough a diaphragm or filter by a solution depends upon the radius ofits capillaries. According to the law of Stokes and Neumann, the speedot discharge of a liquid through a capillary tube is directlyproportional to the fourth power of its radius, The radius of thecapillary tubes in a diaphragm ot this character depends 'upon tirofactors; first, the ratio of the air volume oi the capillary tubes tothe total volume oi the diaphragm; and second, the degree ot suhdivisionoi the ebonite used in making the diaphragms. Since the degree ofsubdivision of the particles may be readily controlled and since, asabove described, it is possible to vary the porosity within Wide limits,I amable to make diaphragms having capillaries Whose radius varies overa Wide range, thus getting' diaphragms or filters ladapted togive anydesired speed of percolation.

`While the chemical composition of the ebonite used for the diaphragmemay vary Within Wide limits and may be selected in accordance With theuse to which the product is to be put, I prefer to employ an ebonitemixture prepared and vulcanized as disclosed in my prior Patent1,022,014, Where the dia-l phragme or iilters are intended to standalkalies and acids. It is particularly important that the thin layerotunvulcanized ebonn ite on the surface of the particles should be ofsuch composition, and that in the process of making the diaphragm thisrubber be overvulcanized. Accelerators may be used so long as they donot have a detrimental influence on the chemical composition of theebonite. The vulcanized ebonite forming' the body of the particlesemployed need not have a long vulcanization since it subsequentlyundergoes a further vulcanization during the manufacture of thediaphragms.

By varying the degree of vulcanization of the particles, and of thediaphragm, the articles may be made pliable in varying degrees. It ispossible to make them of a leather-like consistency and to any otherdegree of hardness desired.

It the diaphragme are desired to Withstand the action of acids andalkalies, the ebonite particles may be covered with the thin layer ofuncured ebonite in the following manner: A solution ot rubber andbenzine with 10 graphite and 35% sulphur is prepared. rlhe particles aremixed in this solution and then separated by filtration. The particlesare dried in Vacuum with recovery of the solvent and are pulverized.This operation may be repeated if necessary.

In carrying out this process, a few parts only of the uncured ebonite ismixed With about 100 parts of the ebonite particles. After the eboniteparticles are mixed with the solution of rubber, benzine, graphite andsulphur, the solution is then removed by evaporation and the mass isheated and dried at about 8O to 1000 C. until the whole of the solventis evaporated and the top surface becernesV dry so that the mass can beseparated into powder by rubbing. rlhe material is then powdered and ifit is desired to coat the ebonite particles with a thicker layer ofuncured ebonite than can be obtained from carrying out the process asabove described, the operation may be repeated if necessary.

instead of covering the ebonite particles with a coating of uncuredebonite, l may cover the ebonite particles with a layer ofnon-vulcanized rubber. ln this case, it is desirable that the eboniteparticles contain free sulphur so that the coating of non-vulcanizedrubber will combine with tl e free sulphur during evaporation andheating. Whether toe ebonite particles are covered with a layer .ofuncured ebonite or with a layer of raw rubber, the process of heatingpartially vulcanizes the coating on the ebonite particles with a layerof material which is more pliable than the ebonite particles. Since thelayer of the semi-vulcanized ebonite or rubber, which coats the solidebonite particles is very thin, it can neither run on heating nor fillup the interstices between the particles.

While l have illustrated and described the preferred embodiment of myinvention, it will be understood that it is not thus limited, as it maybe otherwise embodied or practiced within the scope of the followingclaims.

l claim l. The process of manufacturing porous ebonite bodies whichcomprises bringing ebonite particles having a coatingof uncured eboniteinto such volume that they are in con tact but have interstitial spaces,and vulcanf izing the mass while maintainingits volume substantiallyconstant.

2. The process of making porous ebonite bodies which comprises bringingparticles of ebonite having a coating of uncured ebonite into a moldhaving a greater volume than the aggregate volume of such particles, andvulcanizing the same until an integral porous body `is obtained whilemaintaining its volume substantially constant.

3. The process of making porous ebonite bodies which comprises bringingebonite particles, whose surface portions at least are in an uncuredcondition, into such volume that they are in contact but haveinterstitial spaces, and vulcanizing the mass while maintaining itsvolume substantially constant.

4. A porous ebonite body comprising ebonite particles whose surfaceportions are in-` itially uncured ebonite, the portions occupying suchvolume that adjacent particles are inl Contact but are not compactedinto a nonporous solid mass, the coatings of the particles beingpermanently united by vulcanization between themselves and `with theenclosed ebonite particles.

5. rlhe process of manufacturing porous ebonite bodies which comprisesbringing ebonite particles like powder, shavings and the like, coatedwith a raw rubber compound capable of beingcured into ebonite, in suchvolume as will cause the adjacent particles to sufficiently Contact andcombine, but will not compact Lhem into a solid non-porous mass. andthen vulcanizing them Ainto an 1n-Y hand.

MEYER WILDERMAN.

ER'HFICATE F GRRECHGN.

Patent No. 1,791,437. Granted February 3, 193i, to

MYER WILDERMAN.

it is hereby certified that error appears in the printed specificationet the above numbered patent requiring correction as tnliows: Page 3,line 77, claim 5, aiter the werd "body" insert the words whiiemaintaining its volume substantialiy censtant; and that the said LettersPatent should he read with this cerrection therein that the same mayconform te the record nf the case in the Patent Office.

Signed and sealed this 10th day of March, A. D. 193i.

M. i. Moore, (Saai) Acting Commissioner of Patents.

